1) French word used in English 2) Inalienable 3) Not defeasible 4) Not forfeitable 5) Unforfeitable 1) Undefeasible 2) Unforfeitable 
• (a.) Not to be defeated; not defeasible; incapable of being annulled or made void; as, an indefeasible or title.
Something that cannot be cancelled,changed or undone.It refers to rights in property that cannot be challenged.
In`de·fea`si·ble adjective [ Prefix in- not + defeasible : confer Old French indefaisable .] Not to be defeated; not defeasible; incapable of being annulled or made void; as, an indefeasible or title. « That the king had a divine and an indefeasible right to...
Incapable of being altered or voided, usually used to describe an absolute interest in real estate that cannot be changed.
[adj] - not liable to being annulled or voided or undone
adjective not liable to being annulled or voided or undone; `an indefeasible right to freedom`; `an indefeasible claim to the title`
not defeasible; not to be annulled or made void; not forfeitable.